1. Field of the Invention
The present invention relates to thin-film magnetic heads used for magnetic writing/reading apparatuses and the like.
2. Description of the Related Art
FIGS. 5A and 5B are drawings illustrating a magnetic writing/reading apparatus using a conventional thin-film magnetic head. FIG. 5A is a cross-sectional view of a main portion of the magnetic writing/reading apparatus, and FIG. 5B is a perspective view of a slider. FIGS. 6 to 10 are schematic plan views of trailing side surfaces of the sliders used for conventional thin-film magnetic heads.
In a magnetic writing/reading apparatus such as a hard disk apparatus, a plurality of thin magnetic disks 51 are stacked in spaced relation to one another, and a pair of magnetic heads H facing each other are disposed over and under the magnetic disk 51 therebetween.
As shown in FIGS. 5A and 5B, the magnetic head H comprises a supporting member 52 composed of a leaf spring, a flexible printed circuit, or the like, and two sliders (an upper slider 53a and a lower slider 53b) mounted at the edges of the supporting member 52. Sliders 53a and 53b are composed of a ceramic material, such as aluminum titanium carbide (Al2O3.TiC). An example shown in FIG. 5B is a so-called xe2x80x9ctwo-rail sliderxe2x80x9d (lower slider 53b) having a U-shape in cross-section. On trailing side surface Ta of slider 53a, there are provided head element 54a and four bonding pads 55a1 to 55a4 composed of thin films which work as connecting terminals to peripheral processing circuits (not shown). Similarity to the above, on trailing side surface Tb of slider 53b, there are provided head element 54b and four bonding pads 55b1 to 55b4 composed of thin films which work as connecting terminals to peripheral processing circuits (not shown).
Head elements 54a and 54b are so-called xe2x80x9ccombined thin-film magnetic headsxe2x80x9d comprising magnetoresistive magnetic heads (hereinafter referred to as an MR head) for reading and inductive magnetic heads (hereinafter referred to as an inductive head) for writing laminated on the MR heads. In FIG. 6, the MR heads comprise MR elements (not shown) and conductive layers Ea1 and Ea2, connected to the two ends of one of the MR elements (not shown), and Eb1 and Eb2, connected to the two ends of the other MR element (not shown). Conductive layers at bonding pads 55a4 and 55b4 sides are designated Ea1 and Eb1, respectively. The inductive heads comprise flat helicoid coils Ca and Cb which are composed of a low resistance conductive material, such as nickel (Ni) or copper (Cu), and are covered by insulating layers (not shown).
In individual sliders 53a and 53b, four leads 56a1 to 56a4, and four leads 56b1 to 56b4 are composed of a low resistance conductive material, such as nickel (Ni) or copper (Cu), and are provided at head element 54a side on trailing side surface Ta and at head element 54b side on trailing side surface Tb, as shown in FIG. 6. An end of lead 56a1 is connected to the central edge of coil Ca through an upper connecting lead 57a which is provided on an insulating layer (not shown) so as to pass over coil Ca. An end of lead 56b1 is connected to the central edge of coil Cb through an upper connecting lead 57a which is provided on an insulating layer (not shown) so as to pass over coil Cb. Individual ends of leads 56a2 and 56b2 are connected to the peripheral edges of coils Ca and Cb. Coils Ca and Cb are located at bonding pads 55a4 and 55b4 sides, respectively. Individual ends of leads 56a3 and 56b3 are connected to conductive layers Ea1 and Eb1, which are located at the bonding pads 55a4 and 55b4 sides. Individual ends of leads 56a4 and 56b4 are connected to other conductive layers Ea2 and Eb2, through contact holes (not shown). The other ends of four leads 56a1 to 56a4 are connected to bonding pads 55a1 to 55a4 provided at the upper layers of the leads, and four leads 56b1 to 56b4 are connected to bonding pads 55b1 to 55b4 provided at the upper layers of the leads. Individual bonding pads 55a1 to 55a4, and 55b1 to 55b4, are provided with fine gold wires (not shown), and are connected to peripheral processing circuits (not shown). Signal currents for writing by the inductive heads are fed from bonding pads 55a1 and 55a2, and 55a1 and 55b2, and currents (sense currents) for reading by the magnet heads are fed from bonding pads 55a3 and 55a4, and 55b3 and 55b4.
A method for manufacturing a conventional thin-film magnetic head will be explained. On the MR heads formed on trailing side surfaces Ta of slider 53a and Tb of slider 53b, lower core layers (upper shield layers; not shown) composed of Nixe2x80x94Fe based alloy (Permalloy), layers composed of a non-magnetic material (not shown), and first insulating layers (not shown) are formed, sequentially. Then, coils Ca and Cb composed of copper or the like are formed on the first insulating layers (not shown) by a method of photolithography and plating. In the same step mentioned above, leads 56a1 to 56a4, and 56b1 to 56b4, are formed on the same layers. Leads 56a1 and 56b1 are formed so as to be connected to the peripheral ends of the coil Ca and Cb at the sides thereof. Leads 56a3 and 56a4 are connected through contact holes (not shown) provided beforehand to two conductive layers Ea1 and Ea12 which are connected to one MR element, and leads 56b3 and 56b4 are connected through contact holes (not shown) provided beforehand to two conductive layers Eb1 and Eb2 which are connected to the other MR element. Individual ends of leads 56a2 and 56b2 are disposed at coils Ca and Cb sides, respectively.
Next, second insulating layers (not shown) are formed so as to cover coils Ca and Cb by a method of photolithography after coating an organic resinous material or the like thereon. Contact holes (not shown) leading to the central edges of coils Ca and Cb are provided in the second insulating layers. Then, upper core layers (not shown) are formed on the second insulating layers (not shown) by using Nixe2x80x94Fe based alloy (Permalloy) or the like by a method of frame plating. In the same step mentioned above, individual ends of leads 56a1 and 56b1 are connected to central edges of coils Ca and Cb through contact holes (not shown), and upper connecting leads 57a and 57a are formed so as to pass over coils Ca and Cb. At the other ends of leads 56a1 to 56a4, and 56b1 to 56b4, bumps (not shown) are formed as connecting members with bonding pads 55a1 to 55a4, and 55a1 to 55b4, which are formed later so as to exceed heights of the upper core layers (not shown).
Next, protective layers (not shown) composed of alumina or the like are formed by sputtering so as to cover the upper layers of the upper core layers (not shown), leads 56a1 to 56a4, and leads 56b1 to 56b4. The protective layers are polished until parts of the bumps (not shown) thereunder are exposed, and then, gold bonding pads 55a1 to 55a4, and 55a1 to 55b4, are formed on the exposed bumps (not shown) by plating to complete sliders 53a and 53b. Sliders 53a and 53b are mounted at a supporting member 52 (not shown), then bonding pads 55a1 to 55a4, and 55a1 to 55b4, are connected through fine gold wires (not shown) or the like to flexible printed circuit boards (not shown) which are to be connected to processing circuits; thus, the magnetic head H can be obtained.
In order to write data efficiently on both sides of magnetic disk 51, the magnetic head H is provided with two kinds of sliders 53a and 53b as shown in FIG. 6, in which two head elements 54a and 54b facing each other are located at positions equivalent to each other. Generally, a xe2x80x9cmirrored patternxe2x80x9d is employed for sliders 53a and 53b, in which forms of leads 56a1 to 56a4, and 56b1 to 56b4, winding directions of coil Ca and Cb, and the like are in symmetrical mirror-image relationships.
In conventional magnetic writing/reading apparatuses, such as a hard disk apparatus, writing signals and reading signals of individual magnetic heads H are separately processed by analog processing circuits connected to flexible printed circuits (not shown). At this stage, when polarities of individual electrodes of bonding pads 55a1 to 55a4, and 55a1 to 55b4, are not required to be considered, problems caused by employing the xe2x80x9cmirrored patternxe2x80x9d in the two sliders 53a and 53b facing each other have not occurred.
Recently, in order to improve reliability of signal processing in the magnetic writing/reading apparatus, methods for processing signals from a plurality of magnetic heads by a single digital processing circuit are increasing in use instead of conventional methods for processing signals by a plurality of analog processing circuits connected to individual magnetic heads H. In addition, because of restrictions caused by connecting the digital processing circuits or the like, polarities of electrodes at bonding pads 55a1 to 55a4, and 55a1 to 55b4, are to be determined. Furthermore, when magnetic writing signals are written, directions of currents Iw for writing in coils Ca and Cb, and directions of currents is for reading (sensing) which flow in the MR elements (not shown) through conductive layers Ea1 and Ea2, and through conductive layers Eb1 and Eb2, are required to be in the same directions in some cases.
Due to these recent requirements, when the conventional xe2x80x9cmirrored patternxe2x80x9d is employed for sliders 53a and 53b, and for example, when the polarities of bonding pads 55a1 and 55a2, and 55b1 and 55b2, are determined to be asymmetrical as shown in FIG. 7 (only inductive heads are shown for simplicity), flow directions of currents Iw for writing to the magnetic disk 51 are opposite each other, so that reliability of signal processing cannot be improved.
A method for solving this problem is to change different winding directions of coils Ca and Cb, which are opposite each other due to the conventional xe2x80x9cmirrored patternsxe2x80x9d, to the same winding directions of coils Ca and Cb by employing asymmetric forms, as shown in FIG. 8. By this method, directions of currents Iw for writing can be in the same directions. However, when the connecting point of the peripheral edge of coil Cb and lead 56b2 is at the bonding pad 55b4 side, the number of windings of coil Cb, that is, the total length of Cb, becomes different from that of coil Ca, so that characteristics, such as inductance, of coils Ca and Cb becomes different. Consequently, reliable signal processing cannot be realized.
When the number of windings of the two coils Ca and Cb, are arranged to be equal to each other, the connecting point of the peripheral edge of coil Cb and lead 56b2 is at the side opposite to bonding pad 55b4, so that the form of lead 56b2 must extend over a large area to ensure connection. However, by so extending the form, the total length of leads in upper slider 53a and in lower slider 53b differ from each other, so that divergences of signal intensity and synchronous characteristics occur due to resistance difference described above, and writing errors easily occur.
Sense current Is depends upon the direction of magnetization of the MR element (not shown). For example, when the direction of magnetization of the MR head is from left to right and the polarities of bonding pads 55a3 and 55a4, and 55b3 and 55b4, are determined to be asymmetric as shown in FIG. 10, since sense current Is must flow from left to right, that is, in the transverse direction of the track, forms of bonding pads 55b3 and 55b4 in lower slider 53b must be changed so as to extend. The reason for this is that since leads 56b3 and 56b4 are formed on the same layer, and leads 56b1 and 56b2 are present therebetween, leads 56b3 and 56b4 cannot be extended for the purpose of connection in practice. However, when bonding pads 55b3 and 55b4 are extended in a complicated manner, formation of the forms on trailing side surface Tb of fine slider 53a is complicated and difficult; in addition, the total wiring length of bonding pads 55b3 and 55b4, and leads 56b3 and 56b4 in lower slider 53b differs from that in upper slider 53a. Consequently, the resulting difference in wiring resistance causes divergences of signal intensity and the like between the two sliders 53a and 53b, so that errors easily occur.
As thus described, in order to satisfy requirements for desired directions of writing and reading currents, and requirements for desired polarities of currents flowing through bonding pads in a pair of magnetic heads, forms of leads and bonding pads in conventional thin-film magnetic heads have been arranged depending on winding directions of coils and directions of magnetization of MR elements. However, resistance differences generated by differences of wiring length results in insufficient processing performance for digital processing circuits. Moreover, when leads and bonding pads are formed to satisfy requirements for desired directions of writing and reading currents, and requirements for desired polarities of currents flowing through bonding pads, a number of mask patterns for lithography are required, thereby increasing cost.
Accordingly, in a pair of magnetic heads provided with a magnetic disk for a magnetic writing/reading apparatus, it is an object of the present invention to provide a thin-film magnetic head of which forms of leads are easily changed and characteristics are stable.
As a first solution for solving the problems described above, a thin-film magnetic head according to the present invention comprises an inductive magnetic head for writing having a lower core layer, a coil, and an upper core layer, a first lead connected to the central edge of the coil, and a second lead connected to the coil at the peripheral edge thereof disposed at the side opposite to a writing gap.
Accordingly, when the direction of the current for writing is changed, under the condition that polarities of bonding pads are defined, this can be achieved only by optionally changing a winding direction of the coil, so that leads connected to the coil can be disposed without complicated extension of the leads. Since the length of the coil is not changed, the characteristics, such as inductance, can be consistent, whereby performance in signal processing is ensured. Individual total wiring length of leads and bonding pads is not changed before and after changing a winding direction of the coil, and electrical resistances of individual wirings are equal to each other; therefore, performance of signal processing can be ensured and consistent signal intensity can be obtained. In addition, various requirements for polarities and flow directions of currents for writing can be easily achieved only by changing mask patterns for a photolithographic method used for formation of leads and bonding pads.
As a second solution, a thin-film magnetic head according to the present invention comprises a magnetoresistive magnetic head for reading having a magnetoresistive element, two conductive layers respectively connected to the two ends of the magnetoresistive element, an intermediate lead, an end thereof being connected to one of the conductive layers, the other end being disposed in close proximity to the other conductive layer so that a current flows between a first lead connected to the other end of the intermediate lead and a second lead connected to the other conductive layer.
Therefore, when the direction of the sense current is changed, under the condition that polarities of bonding pads are defined, the change can be achieved, after changing the direction of magnetization of the MR head, by exchanging the lead connected to the conductive layer with the other lead connected to the intermediate lead, without complicated extension of the individual leads. Individual total wiring lengths of leads and bonding pads are not changed before and after exchanging two leads, and electrical resistances of individual wirings are equal to each other, so that performance of signal processing can be ensured and consistent signal intensity can be obtained. In addition, various requirements for polarities and flow directions of sense currents can be easily achieved only by changing mask patterns for a photolithographic method used for formation of leads and bonding pads.
As a third solution, a thin-film magnetic head according to the present invention comprises a magnetoresistive magnetic head for reading having a magnetoresistive element, two conductive layers respectively connected to the two ends of the magnetoresistive element, an inductive magnetic head laminated above the magnetoresistive magnetic head for writing having a lower core layer, a coil, and an upper core layer, a first lead connected to the central edge of the coil, a second lead connected to the coil at the peripheral edge thereof disposed at the side opposite to a writing gap, an intermediate lead disposed on a layer not including the first lead and the second lead, an end thereof being connected to one of the conductive layers, the other end being disposed in close proximity to the other conductive layer, a third lead connected to the other end of the intermediate lead, and a fourth lead connected to the other conductive layer.
Consequently, when the direction of the current for writing is changed, under the condition that polarities of bonding pads are defined, the change can be achieved only by changing the winding direction of the coil, without complicated extension of the individual leads. In addition, when the sense current is changed, under the condition that polarities of bonding pads are defined, the change can be achieved only by connecting the third lead connected to the intermediate lead to the conductive layer, and by connecting the fourth lead connected to the conductive layer to the intermediate lead, without complicated extension of the individual leads. Since the intermediate leads are disposed on a layer not including individual leads, complicated extension of individual leads are not required. Individual total wiring lengths of leads and bonding pads are not changed before and after changing the winding direction of the coil and/or exchanging two leads, and electrical resistances of individual wirings are equal to each other, so that performance of signal processing can be ensured and consistent signal intensity can be obtained. In addition, various combination of, for example, the polarities and the flow direction of sense current, can be easily achieved only by changing mask patterns for a photolithographic method used for formation of leads and bonding pads.
As a fourth solution, a thin-film magnetic unit comprises a thin-film magnetic head according to the present invention, wherein a pair of thin-film magnetic heads faces each other so as to insert magnetic recording medium.
Hence, when the flow direction of the current for writing and/or the flow direction of sense current is changed, under the condition that polarities of bonding pads between two thin-film magnetic head are different, this can be achieved only by changing winding directions of one or two coils, and/or by exchanging a lead connected to the conductive layer and a lead connected to the intermediate lead. Individual total wiring lengths of leads and bonding pads are not changed before and after changing the winding direction of the coil and/or exchanging two leads, and electrical resistances of individual wirings are equal to each other, so that performance of signal processing can be ensured and consistent signal intensity can be obtained. In addition, various combination of, for example, the polarities and the flow direction of sense current, can be easily achieved only by changing mask patterns for a photolithographic method used for formation of leads and bonding pads.